In recent years there has seen a tremendous increase in the demand for wireless networks capable of handling data communications. In order to accommodate this increased demand there is a constant search to find improved, more efficient approaches to communicating subscriber data. One such approach has been to limit the size and content of access requests, sometimes referred to as access bursts. This has the beneficial result of allowing more users to obtain initial access to the channels and, where like some voice cellular systems a dedicated access channel is provided, it permits an operator to keep the number of access channels to a minimum by transferring subscribers obtaining access to a traffic channel.
In the case of non-voice data communications, which are more bursty in nature than traditional voice communications, it is more common to find access and traffic communications taking place on the same channels. It is even more desirable in this case, in order to allow for as many subscribers to get access to this same channel, to keep access burst sizes to a minimum. Consequently, many wireless systems, such as the GSM (Global System for Mobiles) and the proposed GPRS (GSM Packet Radio Service) cellular services, limit their standard access bursts to subscriber identifying information, and essential overhead such as a synch (synchronization) sequence and guard bits. This is also partly because most standard access bursts need the synch sequence and guard bits to be much longer than in traffic bursts. This result occurs because on initial access subscriber timing is not fully synchronized, so a longer training (synch) sequence is needed by the receiving unit. In the case of TDMA (time division multiple access) communications, such as in GSM, the increased guard bits are also needed around the access burst to insure it does not interfere with communications in adjacent time slots.
A major disadvantage with this reliance on standard access bursts is that short data messages cannot be sent through traditional access bursts, and most non-voice communications have a significant amount of such messaging (e.g., ACK (acknowledgment) and NACK (non-acknowledgment) signals). As a result, a common approach in wireless systems has been to require the transmission of an access burst to obtain a channel or subchannel allocation, and then subsequently sending the information in a second burst. Thus three data transfers are required (e.g., two uplink and one downlink allocation) just to send one short message. This inefficiency is complicated by peak loading conditions, when the probabilities of access request collisions are increased by the more limited idle time. Moreover, any solution to this need is further complicated by the desirability of keeping backward compatibility to earlier systems or some level of commonality with related systems like GSM and GPRS.
There remains therefore a need for an improved means for transferring shorter data communications in wireless systems that solves these and related problems.